Developing systems capable of controlled and efficient gene transfer is a fundamental goal of biotechnology, with applications ranging from basic science to clinical medicine. Increasing or decreasing the expression level of a gene within a cell has the power to reveal or confirm the roles of specific components of signaling pathways and can lead to a mechanistic understanding of cell behavior, disease pathogenesis, and drug action. The successful application of gene transfer for basic science and clinical medicine requires the ability to manipulate the expression of target genes in the desired cell population. A variety of approaches are being taken to develop techniques to overcome barriers to gene transfer, which includes processes such as cellular internalization, endosomal escape, and nuclear trafficking.
Cationic polymers provide a versatile approach for gene transfer as the polymers can be designed or modified to overcome some of the current problems encountered with gene transfer. Complexation with cationic polymers functions to condense DNA, to produce a complex with a less-negative surface charge, to enhance cellular internalization of DNA, and to protect the DNA from degradation. Although many types of cationic polymers have been explored (see, for example, van de Wetering et al. (1999) Bioconjug. Chem. 10:589–597), polymers based on poly(L-lysine) (PLL)(see, for example, Choi et al. (1999) Bioconjug. Chem. 10:62–65), poly(ethylenimine) (PEI) (see, for example, Blessing et al. (2001) Bioconjug. Chem. 12:529–537), poly(amidoamine) (PAMAM) (see, for example, Qin et al. (1998) Hum. Gene Ther. 9:553–560), and poly(2-dimethylamino)ethylmethacrylate (p(DMAEMA)) (Arigita et al. (1999) Pharm. Res. 16:1534–1541) are among those utilized.
PEI covalently attached to a biodegradable polymer surface and to surface-immobilized collagen has been used as a gene delivery system. For example, Zheng et al. (2000) Biotechnol. Prog. 16:254–257, created a polymer surface with attached PLL and PEI, to which DNA was non-specifically adsorbed for delivery into a cell.
Recently, polymeric systems originally developed to deliver biologically active proteins have been adapted to deliver non-viral DNA. Polymeric scaffolds have been fabricated from a variety of materials, both natural (e.g., collagen) and synthetic (e.g., poly(lactide-co-glycolide)) which function as a support for cell adhesion and migration. These scaffolds act to increase the local concentration of DNA within the cellular microenvironment either by providing a sustained release of DNA (Shea et al. (1999) Nat. Biotechnol. 17:551–554) or by maintaining the DNA locally (Bonadio et al. (1999) Nat. Med. 5:753–759). Bielinska et al. (2000) Biomaterials 21:877–887 describe the use of a solid support membrane as a device for DNA delivery mediated by PAMAM dendrimers to skin cells. Synthetic systems have also been developed that increase cell-surface concentrations of DNA by adsorbing DNA complexes to the surface (Luo et al. (2000) Nat. Biotechnol. 18:893–895). U.S. Pat. No. 6,312,727 describes a nucleic acid delivery vehicle in which complexes formed from nucleic acids condensed with cationic polymer material are reacted with hydrophilic polymer material to form a hydrophilic coating or shield around the complex.